2 * Hook output functions (like printf(3)) with LD_PRELOAD to color stderr (or
3 * other file descriptors).
5 * Copyright (C) 2013 Simon Ruderich
7 * This program is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program. If not, see <http://www.gnu.org/licenses/>.
23 /* Must be loaded before the following headers. */
24 #include "ldpreload.h"
37 /* Conflicting declaration in glibc. */
38 #undef fwrite_unlocked
41 /* Used by various functions, including debug(). */
42 static ssize_t (*real_write)(int, void const *, size_t);
43 static int (*real_close)(int);
44 static size_t (*real_fwrite)(void const *, size_t, size_t, FILE *);
46 /* Did we already (try to) parse the environment and setup the necessary
48 static int initialized;
49 /* Force hooked writes even when not writing to a tty. Used for tests. */
50 static int force_write_to_non_tty;
53 #include "constants.h"
59 #include "hookmacros.h"
64 /* See hookmacros.h for the decision if a function call is colored. */
67 static void dup_fd(int oldfd, int newfd) {
69 debug("%3d -> %3d\t\t\t[%d]\n", oldfd, newfd, getpid());
72 if (unlikely(!initialized)) {
73 init_from_environment();
76 /* We are already tracking this file descriptor, add newfd to the list as
77 * it will reference the same descriptor. */
78 if (tracked_fds_find(oldfd)) {
79 if (!tracked_fds_find(newfd)) {
80 tracked_fds_add(newfd);
82 /* We are not tracking this file descriptor, remove newfd from the list
85 tracked_fds_remove(newfd);
89 static void close_fd(int fd) {
91 debug("%3d -> .\t\t\t[%d]\n", fd, getpid());
94 if (unlikely(!initialized)) {
95 init_from_environment();
98 tracked_fds_remove(fd);
102 /* "Action" handlers called when a file descriptor is matched. */
104 static char const *pre_string;
105 static size_t pre_string_size;
106 static char const *post_string;
107 static size_t post_string_size;
109 /* Load alternative pre/post strings from the environment if available, fall
110 * back to default values. */
111 inline static void init_pre_post_string(void) {
112 pre_string = getenv(ENV_NAME_PRE_STRING);
114 pre_string = DEFAULT_PRE_STRING;
116 pre_string_size = strlen(pre_string);
118 post_string = getenv(ENV_NAME_POST_STRING);
120 post_string = DEFAULT_POST_STRING;
122 post_string_size = strlen(post_string);
125 static void handle_fd_pre(int fd) {
126 int saved_errno = errno;
128 if (unlikely(!pre_string || !post_string)) {
129 init_pre_post_string();
132 DLSYM_FUNCTION(real_write, "write");
133 real_write(fd, pre_string, pre_string_size);
137 static void handle_fd_post(int fd) {
138 int saved_errno = errno;
140 /* write() already loaded above in handle_fd_pre(). */
141 real_write(fd, post_string, post_string_size);
146 static void handle_file_pre(FILE *stream) {
147 int saved_errno = errno;
149 if (unlikely(!pre_string || !post_string)) {
150 init_pre_post_string();
153 DLSYM_FUNCTION(real_fwrite, "fwrite");
154 real_fwrite(pre_string, pre_string_size, 1, stream);
158 static void handle_file_post(FILE *stream) {
159 int saved_errno = errno;
161 /* fwrite() already loaded above in handle_file_pre(). */
162 real_fwrite(post_string, post_string_size, 1, stream);
169 /* Hook all important output functions to manipulate their output. */
171 HOOK_FD3(ssize_t, write, fd,
172 int, fd, void const *, buf, size_t, count)
173 HOOK_FILE4(size_t, fwrite, stream,
174 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
177 HOOK_FILE2(int, fputs, stream,
178 char const *, s, FILE *, stream)
179 HOOK_FILE2(int, fputc, stream,
180 int, c, FILE *, stream)
181 HOOK_FILE2(int, putc, stream,
182 int, c, FILE *, stream)
183 HOOK_FILE1(int, putchar, stdout,
185 HOOK_FILE1(int, puts, stdout,
188 /* printf(3), excluding all s*() and vs*() functions (no output) */
189 HOOK_VAR_FILE1(int, printf, stdout, vprintf,
190 char const *, format)
191 HOOK_VAR_FILE2(int, fprintf, stream, vfprintf,
192 FILE *, stream, char const *, format)
193 HOOK_FILE2(int, vprintf, stdout,
194 char const *, format, va_list, ap)
195 HOOK_FILE3(int, vfprintf, stream,
196 FILE *, stream, char const *, format, va_list, ap)
197 /* Hardening functions (-D_FORTIFY_SOURCE=2), only functions from above */
198 HOOK_VAR_FILE2(int, __printf_chk, stdout, __vprintf_chk,
199 int, flag, char const *, format)
200 HOOK_VAR_FILE3(int, __fprintf_chk, fp, __vfprintf_chk,
201 FILE *, fp, int, flag, char const *, format)
202 HOOK_FILE3(int, __vprintf_chk, stdout,
203 int, flag, char const *, format, va_list, ap)
204 HOOK_FILE4(int, __vfprintf_chk, stream,
205 FILE *, stream, int, flag, char const *, format, va_list, ap)
207 /* unlocked_stdio(3), only functions from above are hooked */
208 HOOK_FILE4(size_t, fwrite_unlocked, stream,
209 void const *, ptr, size_t, size, size_t, nmemb, FILE *, stream)
210 HOOK_FILE2(int, fputs_unlocked, stream,
211 char const *, s, FILE *, stream)
212 HOOK_FILE2(int, fputc_unlocked, stream,
213 int, c, FILE *, stream)
214 HOOK_FILE2(int, putc_unlocked, stream,
215 int, c, FILE *, stream)
216 HOOK_FILE1(int, putchar_unlocked, stdout,
220 HOOK_VOID1(void, perror, STDERR_FILENO,
225 static void error_vararg(int status, int errnum,
226 char const *filename, unsigned int linenum,
227 char const *format, va_list ap) {
228 static char const *last_filename;
229 static unsigned int last_linenum;
231 /* Skip this error message if requested and if there was already an error
232 * in the same file/line. */
233 if (error_one_per_line
234 && filename != NULL && linenum != 0
235 && filename == last_filename && linenum == last_linenum) {
238 last_filename = filename;
239 last_linenum = linenum;
241 error_message_count++;
245 if (error_print_progname) {
246 error_print_progname();
248 fprintf(stderr, "%s:", program_invocation_name);
250 if (filename != NULL && linenum != 0) {
251 fprintf(stderr, "%s:%u:", filename, linenum);
252 if (error_print_progname) {
253 fprintf(stderr, " ");
256 if (!error_print_progname) {
257 fprintf(stderr, " ");
261 vfprintf(stderr, format, ap);
264 fprintf(stderr, ": %s", strerror(errnum));
267 fprintf(stderr, "\n");
273 void error_at_line(int status, int errnum,
274 char const *filename, unsigned int linenum,
275 char const *format, ...) {
278 va_start(ap, format);
279 error_vararg(status, errnum, filename, linenum, format, ap);
282 void error(int status, int errnum, char const *format, ...) {
285 va_start(ap, format);
286 error_vararg(status, errnum, NULL, 0, format, ap);
292 /* Hook functions which duplicate file descriptors to track them. */
294 static int (*real_dup)(int);
295 static int (*real_dup2)(int, int);
296 static int (*real_dup3)(int, int, int);
300 DLSYM_FUNCTION(real_dup, "dup");
302 newfd = real_dup(oldfd);
304 dup_fd(oldfd, newfd);
309 int dup2(int oldfd, int newfd) {
310 DLSYM_FUNCTION(real_dup2, "dup2");
312 newfd = real_dup2(oldfd, newfd);
314 dup_fd(oldfd, newfd);
319 int dup3(int oldfd, int newfd, int flags) {
320 DLSYM_FUNCTION(real_dup3, "dup3");
322 newfd = real_dup3(oldfd, newfd, flags);
324 dup_fd(oldfd, newfd);
330 static int (*real_fcntl)(int, int, ...);
331 int fcntl(int fd, int cmd, ...) {
335 DLSYM_FUNCTION(real_fcntl, "fcntl");
337 /* fcntl() takes different types of arguments depending on the cmd type
338 * (int, void and pointers are used at the moment). Handling these
339 * arguments for different systems and with possible changes in the future
342 * Therefore always retrieve a void-pointer from our arguments (even if it
343 * wasn't there) and pass it to real_fcntl(). This shouldn't cause any
344 * problems because a void-pointer is most-likely bigger than an int
345 * (something which is not true in reverse) and shouldn't cause
346 * truncation. For register based calling conventions an invalid register
347 * content is passed, but ignored by real_fcntl(). Not perfect, but should
351 result = real_fcntl(fd, cmd, va_arg(ap, void *));
354 /* We only care about duping fds. */
355 if (cmd == F_DUPFD && result != -1) {
362 static int (*real_close)(int);
364 DLSYM_FUNCTION(real_close, "close");
367 return real_close(fd);
369 static int (*real_fclose)(FILE *);
370 int fclose(FILE *fp) {
371 DLSYM_FUNCTION(real_fclose, "fclose");
373 close_fd(fileno(fp));
374 return real_fclose(fp);
378 /* Hook functions which are necessary for correct tracking. */
380 #if defined(HAVE_VFORK) && defined(HAVE_FORK)
382 /* vfork() is similar to fork() but the address space is shared between
383 * father and child. It's designed for fork()/exec() usage because it's
384 * faster than fork(). However according to the POSIX standard the "child"
385 * isn't allowed to perform any memory-modifications before the exec()
386 * (except the pid_t result variable of vfork()).
388 * As some programs don't adhere to the standard (e.g. the "child" closes
389 * or dups a descriptor before the exec()) and this breaks our tracking of
390 * file descriptors (e.g. it gets closed in the parent as well), we just
391 * fork() instead. This is in compliance with the POSIX standard and as
392 * most systems use copy-on-write anyway not a performance issue. */
398 /* Hook execve() and the other exec*() functions. Some shells use exec*() with
399 * a custom environment which doesn't necessarily contain our updates to
400 * ENV_NAME_FDS. It's also faster to update the environment only when
401 * necessary, right before the exec() to pass it to the new process. */
403 static int (*real_execve)(char const *filename, char * const argv[], char * const env[]);
404 int execve(char const *filename, char * const argv[], char * const env[]) {
405 DLSYM_FUNCTION(real_execve, "execve");
410 /* Count arguments and search for existing ENV_NAME_FDS environment
413 char * const *x = env;
415 if (!strncmp(*x, ENV_NAME_FDS "=", strlen(ENV_NAME_FDS) + 1)) {
423 /* Terminating NULL. */
426 char *env_copy[count + 1 /* space for our new entry if necessary */];
427 memcpy(env_copy, env, count * sizeof(char *));
429 /* Make sure the information from the environment is loaded. We can't just
430 * do nothing (like update_environment()) because the caller might pass a
431 * different environment which doesn't include any of our settings. */
433 init_from_environment();
436 char fds_env[strlen(ENV_NAME_FDS) + 1 + update_environment_buffer_size()];
437 strcpy(fds_env, ENV_NAME_FDS "=");
438 update_environment_buffer(fds_env + strlen(ENV_NAME_FDS) + 1);
441 env_copy[index] = fds_env;
443 /* If the process removed ENV_NAME_FDS from the environment, re-add
445 env_copy[count-1] = fds_env;
446 env_copy[count] = NULL;
449 return real_execve(filename, argv, env_copy);
452 #define EXECL_COPY_VARARGS_START(args) \
456 /* Count arguments. */ \
457 size_t count = 1; /* arg */ \
459 while (va_arg(ap, char const *)) { \
464 /* Copy varargs. */ \
465 char *args[count + 1 /* terminating NULL */]; \
466 args[0] = (char *)arg; \
470 while ((x = va_arg(ap, char *))) { \
474 #define EXECL_COPY_VARARGS_END(args) \
476 #define EXECL_COPY_VARARGS(args) \
477 EXECL_COPY_VARARGS_START(args); \
478 EXECL_COPY_VARARGS_END(args);
480 int execl(char const *path, char const *arg, ...) {
481 EXECL_COPY_VARARGS(args);
483 update_environment();
484 return execv(path, args);
487 int execlp(char const *file, char const *arg, ...) {
488 EXECL_COPY_VARARGS(args);
490 update_environment();
491 return execvp(file, args);
494 int execle(char const *path, char const *arg, ... /*, char * const envp[] */) {
495 EXECL_COPY_VARARGS_START(args);
496 /* Get envp[] located after arguments. */
497 char * const *envp = va_arg(ap, char * const *);
498 EXECL_COPY_VARARGS_END(args);
500 return execve(path, args, envp);
503 static int (*real_execv)(char const *path, char * const argv[]);
504 int execv(char const *path, char * const argv[]) {
505 DLSYM_FUNCTION(real_execv, "execv");
507 update_environment();
508 return real_execv(path, argv);
511 static int (*real_execvp)(char const *path, char * const argv[]);
512 int execvp(char const *path, char * const argv[]) {
513 DLSYM_FUNCTION(real_execvp, "execvp");
515 update_environment();
516 return real_execvp(path, argv);